So i figured out what the problem was. In my initialize(), which is called
when the factory is first loaded, it does a require() on Plugin, which does
a require() on PluginAction, which does a require() on PluginFactory. So
the PluginFactory is require()'d before the first require() is finished. So
I made the initialize() a public method and call it in my app.js when the
application starts. Now everything works fine.
Regarding your advice about manipulating the JSON. I do not manipulate the
original object but instead make a copy of it with the modified plugin
variable. Ofcourse when converting back to JSON, I still need to change
this variable back to the original object. In my opinion this was the
only/best method to achieve the desired result. If you are curious I could
post the toJOSN() and fromJSON() implementation here.
Op dinsdag 25 maart 2014 21:35:25 UTC+1 schreef Sam IT:
>
> Your implementation works on my end. The object is cached, see the output
> below:
>
> -------
> samit@random:~/temp$ cat test.js
> var a = require('./plugin-factory').PluginFactory,
> b = require('./plugin-factory').PluginFactory,
> c = (a === b);
>
> console.log(c);
> samit@random:~/temp$ node test.js
> PluginFactory initialized
> true
> samit@random:~/temp$
> -------
>
> What version of node.js are you running?
>
> Are you sure that the factory object isn't cached when you require() it?
> How did you reach that conclusion? (Does it print "PluginFactory
> initialized" multiple times?)
>
> --
>
> Finally, I'm not sure if changing PluginAction's "plugin" property (when
> you serialize/deserialize it) is the best way to accomplish what you're
> trying to do.
>
> Logically speaking, when you serialize an object (ObjectA), you
> essentially create a representation (ObjectB) of ObjectA. I would avoid
> modifying ObjectA and instead make the necessary changes in ObjectB, since
> this is when and where those changes are needed. For this reason (and
> others), I think it's clearer and may help avoid issues but this is just my
> general opinion.
>
>
> On Tue, Mar 25, 2014 at 9:41 AM, <[email protected] <javascript:>> wrote:
>
>> I realised the problem is completely different, because of my
>> implementation of Singleton, the Factory is not saved/cached in the GLOBAL
>> variable (which all required() variables usually are, it seems). So my
>> guess now it has to do with my implementation of the Singleton pattern:
>>
>> var PluginFactory = (function() {
>> /**
>> * Actual implementation of the class.
>> * This is encapsulated because the class is a singleton.
>> */
>> function PluginFactory() {
>> // Implementation using prototype functions
>> }
>>
>> /**
>> * This variable holds the singleton instance of the factory class.
>> */
>> var instance = null;
>>
>> function initialize() {
>> console.log("PluginFactory initialized");
>> }
>>
>> /**
>> * This method returns a singleton instance of the factory.
>> */
>> return {
>> getInstance: function() {
>> if (instance === null) {
>> // Create a new instance and hide its constructor
>> instance = new PluginFactory();
>> instance.constructor = null;
>> initialize();
>> }
>>
>> return instance;
>> }
>> };
>> })();
>>
>> // Export a singleton instance of the PluginFactory
>> exports.PluginFactory = PluginFactory.getInstance();
>>
>>
>> Any thoughts why this implementation isn't handled like i expect?
>>
>> Op dinsdag 25 maart 2014 13:50:27 UTC+1 schreef [email protected]:
>>
>>> Hi,
>>>
>>> So i'm having problems with my architecture of my node application, I
>>> know the problem, I'm just trying to find the best solution.
>>>
>>> My problems is exactly the same as: https://groups.google.com/
>>> forum/#!topic/nodejs/u_9IE2z_6rM
>>>
>>> Only I'm using a Factory class to create plugins of the type "IPlugin".
>>> These plugins have certain actions, called PluginAction.
>>>
>>> A PluginAction has a field plugin, which refers to its parent plugin.
>>> When serializing to JSON, i replace the plugin object with a string
>>> identifier, pointing to the correct plugin.
>>>
>>> My PluginFactory can retrieve a plugin using retrieve(identifier). The
>>> problem occurs when I try to deserialize a given PluginAction.
>>>
>>> At that point I would like to convert the plugin identifier back to the
>>> plugin object, by retrieving it from the Factory. This is where it goes
>>> wrong.
>>>
>>> I understand this could be a bit hard to follow, so I've included a part
>>> of my class diagram, which might clarify it more. Short summary:
>>>
>>>
>>> 1. PluginFactory.initialize() loads all plugins in a certain
>>> directory using require()
>>> 2. PluginAction.toJSON() changes the plugin object to a string
>>> containing the plugin identifier
>>> 3. PluginAction.fromJSON() when trying to retrieve the plugin object
>>> using the PluginFactory, I cannot load the PluginFactory file.
>>>
>>> --
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